1. Technical Field
This invention relates generally to gaskets for use in internal combustion engines, and more particularly to a gasket for an internal combustion engine having replaceable cylinder liners (for example, heavy-duty diesel engines).
2. Related Art
The pressures in the combustion chamber of an internal combustion engine have a tendency to flex the cylinder head upwardly, except at the location where the cylinder head is bolted to the engine block. Typically, the bolts are spaced away from the combustion chambers of the engine. As a result, the pressures of combustion flex the cylinder head away from the engine block in a region between the bolts and the combustion chamber, producing a gap. In an engine having combustion chamber liners sealed to the cylinder head, as combustion forces unload, there is, because of this gap, a tendency for the forces to drive through the seal and the liner, rather than into the block through the tightly clamped, bolted region. This results in liner movement and wear of the seal.
A gasket constructed according to the invention includes a gasket plate adapted to be installed between an engine block having a combustion chamber fitted with a liner and a liner seal, and a cylinder head which is bolted to the block at locations spaced from the combustion chamber. The plate has bolt holes for the bolts and an opening surrounding the combustion chamber. An annular thickened portion of the plate is provided immediately adjacent the opening. The thickened portion takes up the gap that forms between the head and block when combustion pressures flex the portion of the cylinder head inwardly of the bolts away from the block. The thickened portion further serves to limit the load on the liner seal and provides a direct unloading path from the head to the block for transmitting the unloading forces as the head portion recovers following flexing.
In one embodiment of the present invention the thickened portion is spaced laterally outwardly of the liner seal and may be provided by an incompressible metal or sintered metal ring which overlies an edge of the gasket around the opening. The effect of this enlarged or thickened portion of the gasket is to serve as a load limiter to limit the load on the liner seal, to take up the gap, and to provide a path for unloading forces generated in the combustion chamber to the engine block. The result is significantly less liner movement and reduced wear on the seal.
In another embodiment of the invention, the gasket comprises a metal carrier plate sandwiched between parallel metal cover plates formed with embossments or sealing beads. The plates of the gasket cooperate to form a seal between the liner and the cylinder head. The carrier plate has an enlarged or thickened portion radially outwardly of the combustion chamber. The enlarged or thickened portion of the carrier plate, in cooperation with the cover plates, has the same general function as the enlarged or thickened portion previously referred to, that is to serve as a load limiter, to take up the gap that may form between the engine block and the cylinder head, and to provide a path for unloading forces generated in the combustion chamber to the engine block. Another thickened portion of the carrier overlies the liner and cooperates with the outer layers to form a seal for the liner.
In addition to the above objects and advantages, the gasket has the further advantages of being of relatively simple construction, rugged and durable in use, being inexpensively manufactured and easily installed.
These and other objects, features and advantages of the invention will become more apparent when considering the following description and accompanying drawings.